Batteries go dead in about 3 days, there's a short somewhere.

Could be many things. Cooked batteries, an accessory left on, failed alternator etc.

 

Sat. radio left wired on or any other ele. logging box wired up to stay on all the time?

 

Batteries have a life span, some last longer than others.
A good solid system will have a strong alternator, good wires and solid connections.

Would guess that the system has a bad battery. May be a shorted / dead cell. Could be sulfated and the plates are now breaking down. The reasons are numerous as to why the system is not holding up.

In order to test the system, all the batteries need to be disconnected from the system, charge and capacity tested. They do need to be checked individually, otherwise the testing is on the group. That is not a valid test result. Only when your batteries are known good, fully charged and the wiring and connections are clean and correct can you then test the start and charging system.

Once that portion of the system is confirmed to be operational and fully feeding the load and system, you can then look at static load and power draw or other losses.

 

Second everyone on everything! I would start something like this. If your truck has been parked for 6 hours and the alternator is still warm to the touch it is bad and discharging the batteries. When you come in off the road for three or more days disconnect all the batteries from each other. One bad battery can discharge all the others. Then test the batteries individually.

 

Does it smell like horrible eggs? Mine did that after they exploded.

 

After they exploded, would have thought it was just before they explode.

When a battery is charging (lead-acid type) it gives off a small amount of hydrogen gas. Hydrogen at about 4.5 percent concentrated can be explosive. It is rare but can happen. The other gas from batteries is hydrogen sulfide.
This is gas produces the sort of rotten egg smell from a battery. Usually this occurs for these reasons. First, the battery is getting over charged. This is an electrical system problem. Overcharging boils the water out of the electrolytes of the battery, then it starts the breakdown of the plates. Once this starts, not much you can do but replace battery.

 

Ya what he said ^

 

I hate when that happens!!